My Charlie used a litter box also. The advice you got was great, they respond well to treats too. Give her one if she goes in the box along with lots of praise. If she has an accident she doesn't get a treat. If you catch her going or about to go rush her to the box right away. I would catch him and rush him to the box even if he'd pretty much finished. Also when I put him in the box I would say "go potty", now he knows what it means and it works even outside. One thing I found was it had to be very clean (I had to pick up after him right away) or he would go on the floor next to it. You may have a very picky puppy or she may have just not quite figured it out yet. It was great having the litter box during the winter but now Charlie prefers to go outside. But if he's home alone he'll still use the box. Good Luck!